Study Finds Unique Emotional Regulation Deficits in Bipolar I Disorder
A new study published in the journal Bipolar Disorders finds some emotional regulation deficits linked to bipolar I disorder (BD-I) may be unique to the condition and not present in bipolar II disorder (BD-II).
In the findings, both groups exhibited emotional reactions during an attention control test in the presence of emotional distractions, but BD-I patients alone showed evidence of behavioral, functional, connectivity, and white matter microstructure deficits not found in patients with BD-II.
The findings “emphasize deficient emotion regulation in the pathophysiology of the disorder, but suggest important differences between BD-I and BD-II in this process”, explained the team, led by Xavier Caseras from Cardiff University in the UK.
The study recruited three groups; one comprised of 16 euthymic patients with BD-I, one including 19 euthymic patients with BD-II, and 20 mentally healthy control participants. All were asked to complete a 2-back working memory task, during which targets were occasionally accompanied with two identical emotional facial expressions of fear, happiness, or a neutral expression.
These emotional distractions significantly slowed the reaction times for participants with BD-I compared to both the healthy group and the patients with BD-II. Most significantly, the average reaction time of BD-I patients slowed from approximately 680 msec with no distractors to 775 msec in the presence of fear expressions. This change was not found in participants with BD-II.
The findings showed that both groups of patients with bipolar disorder showed increased blood oxygenation level-dependent (BOLD) responses in the dorsolateral prefrontal cortex (DLPFC) and amygdala during the presence of fear distractors compared with healthy controls. However, only BD-I patients showed increased inverse functional connectivity between these regions between the DLPFC and amygdala. Conversely, BD-II patients actually showed heightened functional connectivity in these regions in the presence of fear distractors.
The study also found BD-I patients showed reduced fractional anisotropy in the right uncinated fasciculus, compared with BD-II and healthy controls.
“This finding further supports emotion regulation circuitry abnormalities being specific to BD-I and not generalized to BD-II”, wrote the researchers.
The findings indicated that “the less compromised the white matter in the uncinate fasciculus, as in subjects with BD-II relative to subjects with BD-I, the better the functional DLPFC–amygdala coupling during emotion regulation, resulting in better task performance”, they add.